Extreme environments pose a challenge to sensors configured to monitor a parameter in its surrounding environment. For instance, high temperature environments, high pressure environments, and/or environments containing corrosive gases all pose challenges for designing a sensor capable of sustained operation in such extreme environments. In view of these challenges, use of conventional sensors is either not viable in such environments, or requires modification such as a large and cumbersome size, e.g. due to one or more surrounding layers to protect the sensor from the surrounding extreme environment. For example, conventional sensors for use at high temperature are often designed to mitigate the effects of high temperature upon the sensors, such as by minimizing the flow of heat from the surrounding high temperature environment to the sensor.
Thermionic emission is a phenomenon in which heat induces the generation and flow of electrons from a metal surface. The flow of electrons occurs when the thermal energy of an electron is greater than the binding force of the electron to the metal (i.e., the thermal energy exceeds the work function of the metal). Thermionic emission, as a phenomenon, has been utilized in conventional devices, such as in vacuum tubes, where released electrons are collected on a positively charged anode. For example, some conventional devices include a heating coil to heat a metal surface to a sufficient temperature for thermionic emission to occur. For instance, the cathode is heated up with an external power source, but the anode is not. The enclosure remains in normal low temperature ambient conditions.
It would thus be useful to provide a sensor that can take advantage of the surrounding environment to facilitate its function, which would be capable of sensing a wide range of relevant process conditions, such as, for example, temperature, pressure, strain, flux, or flow rate. By providing a sensor for sustained use in an extreme environment, enhanced monitoring and control may be provided for systems subject to the extreme environment.